John D. Inazu, Washington University, St. Louis, School of Law, is publishing The First Amendment's Public Forum in the William and Mary Law Review (2015). Here is the abstract.

The quintessential city park symbolizes a core feature of a democratic polity: the freedom of all citizens to express their views in public spaces free from the constraints of government imposed orthodoxy. The city park finds an unlikely cousin in the federal tax code’s recognition of deductions for contributions made to charitable, religious, and educational organizations. Together, these three categories of tax-exempt organizations encompass a vast array of groups in civil society. The resulting mosaic is neither thematic nor tidy, but it is in at least one sense, beautiful: the deductions, like the city park, enact the aspirations of a democratic polity. Organizations and ideas wither or thrive not by government fiat but based on the “values and choices of private givers.” The city park is a traditional public forum under First Amendment doctrine, and the charitable, educational, and religious deductions under the federal tax code function much like a limited public forum. Between these poles lie numerous other governmental arrangements with similar purposes and functions: sidewalks, parking lots, public schools, websites, public libraries, vanity license plates, and student activity funds, to name a few. In each of these cases, private groups and individuals rely on government resources (financial or otherwise) to inculcate and express their ideas and their ways of life. The ideal of the public forum represents one of the most important aspects of a healthy democracy. It signifies a willingness to tolerate dissent, discomfort, and even instability. The distortion of that ideal represents one of the greatest challenges to First Amendment jurisprudence today. That distortion is partially attributable to two important doctrinal developments. The first is increased judicial reliance on purportedly “content-neutral” time, place, and manner restrictions. The second is the relationship between the public forum and the evolving government speech doctrine, under which the government characterizes messages advanced under the auspices of its financial and other resources as distinctively its own and not subject to First Amendment review. This essay suggests that one factor facilitating these developments is a gradual but unmistakable shift in the moorings of the public forum doctrine from the Assembly Clause to the Speech Clause. The public forum is a First Amendment doctrine, not a free speech doctrine. And we will only comprehend its purposes and its possibilities when we rediscover the values underlying the rights of the First Amendment.